This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The hypothesis for this study is that oral naltrexone will improve inflammation of the bowel by increasing endogenous enkephalin levels in subjects with active Crohn's disease.